opening

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act or an instance of becoming open or being made to open.
• noun A gap, breach, or aperture.
• noun A clearing in the woods.
• noun The first part or stage, as of a book.
• noun The first performance.
• noun A formal commencement of operation.
• noun A specific pattern or series of beginning moves in certain games, especially chess.
• noun An opportunity affording a chance of success. synonym: opportunity.
• noun An unfilled job or position; a vacancy.

from The Century Dictionary.

• noun The act of making open, in any sense of the verb open.
• noun A beginning; an initial stage; commencement: as, the opening of a poem; also, dawn; first appearance.
• noun A breach or gap; a hole or perforation; an aperture; specifically, in architecture, an unfilled part in a wall left for the purpose of admitting light, air, etc.
• noun An open or clear space affording approach, entrance, or passage; an entrance.
• noun A clear, unobstructed, or unoccupied space or place; specifically, in the United States, a tract over which there is a deficiency of forest, trees being not entirely wanting, but thinly scattered over the surface as compared with their abundance in an adjacent region.
• noun A widening out of a crevice, in consequence of a softening or decomposition of the adjacent rock, which may still remain partly or wholly in its original position, or may have been entirely removed, so as to leave a vacant space of considerable width.
• noun An unoccupied place, position, course of action, business, etc., which may be entered, or the opportunity of entering it; a vacancy; an opportunity; a chance.
• noun In law, the statement of the case made by counsel to the court or jury preliminary to adducing evidence: as, the opening for the plaintiff; the opening for the defendant.
• noun In chess-playing, a mode of commencing a game; specifically, one of the numerous series of consecutive moves made at starting which are frequently played and which have been thoroughly investigated by chess analysts.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act or process of opening; a beginning; commencement; first appearance.
• noun A place which is open; a breach; an aperture; a gap; cleft, or hole.
• noun colloq. An opportunity.
• noun A vacant place; a job which does not have a current occupant.
• noun U.S. A thinly wooded space, without undergrowth, in the midst of a forest; a clearing.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb Present participle of open.
• noun An act or instance of making or becoming open.
• noun Something that is open.
• noun An act or instance of beginning.
• noun Something that is a beginning.
• noun A vacant position, especially in an array.
• noun An opportunity, as in a competitive activity.
• adjective cricket describing the first period of play, usually up to the fall of the first wicket; describing a batsman who opens the innings or a bowler who opens the attack

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a recognized sequence of moves at the beginning of a game of chess
• noun the initial part of the introduction
• noun an entrance equipped with a hatch; especially a passageway between decks of a ship
• noun the first of a series of actions
• noun the first performance (as of a theatrical production)
• noun an aperture or hole that opens into a bodily cavity
• noun a ceremony accompanying the start of some enterprise
• noun opportunity especially for employment or promotion
• noun the act of opening something
• noun a possible alternative
• noun an open or empty space in or between things
• noun a vacant or unobstructed space that is man-made
• noun becoming open or being made open
• adjective first or beginning